Britain’s government on Monday condemned as “thuggish” hundreds of demonstrators who blocked roads, vowing to prevent asylum seekers from leaving the southern English city of Portsmouth after they arrived by small boat.

The protest on Sunday night was the second significant anti-migrant demonstration of the weekend after large crowds of masked men blocked access to the Port of Dover on Saturday.

“We condemn the intimidating and thuggish behaviour we saw in Portsmouth last night,” a spokesperson for the UK interior ministry, known as the Home Office, said in a statement.

“The right to peaceful protest is fundamental to our democracy, but it must never cross a line into disorder.”

Social media footage showed the demonstrators, many dressed in black and with their faces covered, squaring up to police officers carrying riot shields.